Semiconductor light-emitting apparatus and method of fabricating the same

ABSTRACT

A light-emitting apparatus has a light-emitting device and a supporting board. The light-emitting device has a pair of n-electrodes with a p-electrode therebetween, on the same plane. The supporting board includes an insulating substrate on which positive and negative electrodes are formed, opposing to the p- and n-electrodes of the light-emitting device, respectively. Bonding members bond the p- and n-electrodes with the positive and negative electrodes, respectively. The positive electrode on the supporting board is formed within the width region of the p-electrode and narrower in width than the width of the p-electrode, in a cross-section along a line extending through the pair of n-electrodes. The negative electrodes oppose to the n-electrodes, respectively, with the same widths, or with that side face of each of the negative electrodes which faces the positive electrode being retracted outwardly from that side face of each of the n-electrodes which faces the p-electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of Ser. No. 12/615,479filed Nov. 10, 2009, now U.S. Pat. No. 8,450,764, which in turn is basedupon and claims the benefit of priority from prior Japanese PatentApplication No. 2008-291259, filed Nov. 13, 2008, the entire contents ofeach of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light-emittingapparatus and a method of fabricating the same, and more specifically,to a semiconductor light-emitting apparatus in which a semiconductorlight-emitting device is mounted on a supporting board by bondingmembers.

2. Description of the Related Art

A surface-mounted light-emitting apparatus using a semiconductorlight-emitting device chip (hereinafter referred to as “light-emittingdevice”) such as a light-emitting diode (LED) or a laser diode is knownin the art. As such an apparatus, there is known an apparatus in which alight-emitting device having p- and n-electrodes on the same side isflip chip-mounted on an insulative supporting board on which a wiringpattern including positive and negative electrodes is formed, in orderto enhance the light extraction efficiency. In this case, a solderpaste, such as an AuSn solder paste, is applied on a predetermined areaof the supporting board on which the positive and negative electrodesare formed, a light-emitting device provided with an Au bump is flipchip-mounted on the supporting board, and then, the solder is reflowed.Peripheral portions of the light-emitting device and the bump are sealedwith a light-transmitting sealing resin.

The light-emitting apparatus of the above structure exhibits strongbonding strength and has a superior reliability, since thelight-emitting device and the supporting board is bonded with the Aubump, which has a certain level of height. However, because of theheight of the bump, the sealing resin intervenes between thelight-emitting device and the supporting board in a large amount. Whenthe intervening resin is subject to thermal stress, the stressprogresses from the wiring pattern to the light-emitting device. Whenthe amount of the intervening resin is large, or when the light-emittingapparatus of the above structure is used in an environment involvingsever change in temperatures, this stress becomes so strong as toadversely affect the adhesion between the light-emitting device and thesealing resin or the bonding between the light-emitting device and thewiring pattern, resulting in lowering of reliability by the absorptionof moisture and in poor bonding of the light-emitting device, leading tonon-lighting of the light-emitting device.

On the other hand, a light-emitting apparatus has been proposed in theart, in which a light-emitting device is mounted on a supporting boardby means of a bonding member other than an Au bump. However, when thedistance between the light-emitting device and the supporting boardbecomes small, it is necessary to take measures to preventshort-circuiting between the p- and n-electrodes on the light-emittingdevice and between the positive and negative electrodes on thesupporting board.

Jpn. Pat. Appln. KOKAI Publication No. 2005-38892 discloses, for thepurpose of preventing short-circuiting between p- and n-electrodes on alight-emitting device and between p-type and n-type compoundsemiconductor layers, forming a recess or groove in a boundary regionbetween the positive and negative electrodes on the supporting board.The solder, heated and compressed between the light-emitting device andthe supporting board and tending to run off from between thelight-emitting device and the supporting board, flows into the recess,whereby the short-circuiting between the positive and negativeelectrodes by the solder is prevented. However, when the distancebetween the p- and n-electrodes is made small to increase output poweror when the n-electrode on the light-emitting device is made smaller,volume of the recess sufficient to prevent the short-circuiting can notbe acquired, leading to the short-circuiting between the two electrodeson the light-emitting device by the solder.

Further, Jpn. Pat. Appln. KOKAI Publication No. 2008-4948 discloses, inFIG. 1, that in a face down-mounted LED device, the distance betweenpositive and negative electrodes on a submount is broader than thedistance between p- and n-electrodes on a light-emitting device.However, if the p-electrode on the light-emitting device is arrangednear the positive electrode on the submount, the p-electrode on thelight-emitting device is short-circuited with the negative electrode onthe submount when the bonding is effected by means of an electricallyconductive material.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light-emittingapparatus in which electrodes of a light-emitting device and electrodesof a supporting board are bonded with a bonding member or members andwhich can prevent unnecessary short-circuiting between the electrodes bythe bonding member(s) and thus can be fabricated with good yield, aswell as a method of fabricating such a light-emitting apparatus.

According to a first invention, there is provided a method offabricating a semiconductor light emitting apparatus comprising asemiconductor light-emitting device having an electrode formation planeand comprising p- and n-electrodes in the electrode formation plane; asupporting board comprising an insulating substrate which has anelectrode formation plane corresponding to the electrode formation planeof the light-emitting device and on which positive and negativeelectrodes are formed so as to oppose to the p- and n-electrodes of thelight-emitting device, respectively; and bonding members bonding the p-and n-electrodes with the positive and negative electrodes,respectively, the method comprising: supplying a bonding material in apaste state onto the electrode formation plane of the supporting boardincluding the positive and negative electrodes; placing thelight-emitting device on the bonding material such that the p- andn-electrodes of the light-emitting device contact the bonding material;and heating and melting the bonding material, thereby bonding the p- andn-electrodes on the light emitting device with the positive and negativeelectrodes on the supporting board, respectively.

According to a second invention, there is provided a semiconductorlight-emitting apparatus comprising: a semiconductor light-emittingdevice having an electrode formation plane and comprising a p-electrodeand a pair of n-electrodes with the p-electrode therebetween, formed inthe electrode formation region; a supporting board supporting thelight-emitting device and comprising an insulating substrate which hasan electrode formation plane corresponding to the electrode formationplane of the light-emitting device and on which a positive and a pair ofnegative electrodes are formed in the electrode formation plane of thesupporting board, electrically isolated from each other and opposing tothe p- and n-electrodes on the light-emitting device, respectively; andbonding members bonding the p-electrode and the n-electrodes of thelight-emitting device with the positive electrode and the negativeelectrodes of the supporting board, respectively; the p-electrode of thelight-emitting device being formed substantially entirely on theelectrode formation plane of the light-emitting device, except for thoseportions on which the n-electrodes are formed, and being eutecticallybonded with the positive electrode of the supporting board; the positiveelectrode on the supporting board being formed within a width region ofthe p-electrode and narrower in width than the width of the p-electrode,in a cross-section along a line extending through the pair ofn-electrodes on the light-emitting device; the negative electrodes onthe supporting board opposing to the n-electrodes of the light-emittingdevice, respectively, with the same widths, or with that side face ofeach of the negative electrodes which faces the positive electrode beingretracted outwardly from that side face of each of the n-electrodeswhich faces the p-electrode.

According to a third invention, there is provided a semiconductorlight-emitting apparatus comprising: a semiconductor light-emittingdevice having an electrode formation plane and comprising an n-electrodeand a pair of p-electrodes with the n-electrode therebetween, formed inthe electrode formation region; a supporting board supporting thelight-emitting device and comprising an insulating substrate which hasan electrode formation plane and on which a negative and a pair ofpositive electrodes are formed in the electrode formation plane of thesupporting board, electrically isolated from each other and opposing tothe n- and p-electrodes on the light-emitting device, respectively; andbonding members bonding the p-electrode and the n-electrodes on thelight-emitting device with the positive electrode and the negativeelectrodes on the supporting board, respectively; that side face of eachof the positive electrodes which faces the negative electrode beingretracted outwardly from that side face of each of the p-electrodeswhich faces the n-electrode, and the negative electrode of thesupporting board being opposed to the n-electrode on the light-emittingdevice with the same width or with a narrower width in a cross-sectionalong a line extending through the pair of p-electrodes on thelight-emitting device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross-sectional view schematically illustrating asemiconductor light-emitting apparatus according to a first embodimentof the present invention;

FIG. 2 is a cross-sectional view schematically illustrating thesemiconductor light-emitting device constituting the semiconductorlight-emitting apparatus illustrated in FIG. 1;

FIG. 3 is a plan view illustrating the plane in which the electrodes ofthe semiconductor light-emitting device illustrated in FIG. 2 areformed;

FIG. 4 is a plan view illustrating the plane in which the electrodes ofthe supporting board constituting the semiconductor light-emittingapparatus illustrated in FIG. 1 are formed;

FIG. 5 is a graph illustrating a relationship between a thermalresistance ratio and a proportion or ratio of a bonding area of thepositive electrode of the supporting board with the bonding member to abonding area of the p-electrode of the light-emitting device with thebonding member;

FIG. 6 is a plan view illustrating another electrode pattern on theelectrode formation plane of the light-emitting device illustrated inFIG. 1;

FIG. 7 is a cross-sectional view schematically illustrating asemiconductor light-emitting apparatus according to a second embodimentof the present invention;

FIG. 8 is a cross-sectional view schematically illustrating asemiconductor light-emitting apparatus according to a third embodimentof the present invention;

FIG. 9 is a plan view illustrating an example of an electrode pattern onthe electrode formation plane of the light-emitting device illustratedin FIG. 8; and

FIG. 10 is a plan view illustrating an example of an electrode patternon the electrode formation plane of the supporting board illustrated inFIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

Some of embodiments of the present invention will be described belowwith reference to the accompanying drawing FIGURES. However, theseembodiments are only exemplary, embodying the technical idea of thepresent invention, and are not intended to limit the present invention.Further, these embodiments are not intended to the materials or elementsrecited in the appended claims to those describe in these embodiments.In particular, the dimensions, materials, shapes or other relativearrangements of the members or elements described in these embodimentsare not intended to limit the invention thereto unless so specifiedtherein, and are only exemplary. Note that the sizes and the positionalrelationship illustrated in the accompanying drawing FIGURES are not toscale, and are exaggerated in order to described them more clearly insome cases. Further, in the following descriptions, the same or similarmembers or elements are indicated by the same or similar referencesymbols, and the detail explanation for them are omitted in some cases.Furthermore, a plurality of elements constituting the invention may beconstructed from one member, or a plurality of functions of a singleelement constituting the invention may be shared by a plurality ofmembers.

First Embodiment

FIG. 1 is a cross-sectional view schematically illustrating the mainpart of a semiconductor light-emitting apparatus according to a firstembodiment of the invention. FIG. 2 is a cross-sectional viewschematically illustrating the semiconductor light-emitting deviceconstituting the semiconductor light-emitting apparatus illustrated inFIG. 1. FIG. 3 is a plan view illustrating the plane in which theelectrodes of the semiconductor light-emitting device illustrated inFIG. 2 are formed. FIG. 4 is a plan view illustrating the plane in whichthe electrodes of the supporting board constituting the semiconductorlight-emitting apparatus illustrated in FIG. 1 are formed. Here, FIG. 1(also FIG. 2) corresponds to a cross-section along the line I-I of FIG.3 which extends through a pair of n-electrodes and p-electrodeillustrated in FIG. 3.

The semiconductor light-emitting apparatus illustrated in FIG. 1comprises a semiconductor light-emitting device 10 and a supportingboard 20. If necessary, the light-emitting device 10 may be sealed by alight-transmitting sealing member 40 in order to protect thelight-emitting device 10 from outside force from the outsideenvironment, dusts and moisture, and the like. The sealing member isfilled also in the space between the light-emitting device 10 and thesupporting board 20.

The light-emitting device 10 comprises a light-transmitting insulativesubstrate 11, a semiconductor laminate structure 12 including an n-typesemiconductor layer, an active (or light-emitting) semiconductor layerand a p-type semiconductor layer, formed on the substrate 11, and ap-electrode 13 and a pair of main n-electrode 14 a and 14 b, formed onthe laminate structure 12.

As illustrated in more detail in FIG. 2, the semiconductor laminatestructure 12 illustrated in FIG. 1 comprises an n-type semiconductorlayer 121, formed on the substantially entire surface of the substrate11, an active layer 122, formed on the substantially entire surface ofthe n-type semiconductor layer 121, and a p-type semiconductor layer123, formed on the substantially entire surface of the active layer 122.The p-type semiconductor layer 123 and the active layer 122 arepartially removed to expose portions of the surface of the n-typesemiconductor layer 121, for forming the n-electrodes 14 a and 14 b. Itis preferred that an insulating protective film 15 (see FIGS. 2 and 3;not illustrated in FIG. 1) is formed on the exposed surface portion ofthe n-type layer 121, except for the surface portions on which then-electrodes 14 a, 14 b are formed. The protective film 15 also coversthe side surfaces of the n-electrodes 14 a and 14 b, the side surface ofthe p-electrode 13, the peripheral portion of the surface of each of then-electrodes 14 a and 14 b, and the peripheral portion of the surface ofthe p-electrode 13. The protective film 15 may be formed of an oxide(e.g., silicon dioxide) or a nitride (e.g., silicon nitride). Thethickness of the protective film 15 may be, e.g., 0.2 μm or more andusually 1.5 μm or less. Incidentally, in the state of FIG. 2, usually,the lower surface of the p-electrode 13 protrudes slightly (e.g., about1-2 μm) from the lower surface of each of the n-electrodes 14 a and 14b. However, this protrusion does not cause any problem for the purposesof the present invention.

The light-emitting device 10 may be any semiconductor light-emittingdevice. For example, a semiconductor laser or a semiconductor LED may beused. When the light-emitting device 10 is an LED, the semiconductorlaminate structure 12 comprising the n-type semiconductor layer 121, theactive layer 122 and the p-type semiconductor layer 123 is preferablyformed on a sapphire substrate (light-transmitting insulative substrate11), which makes it possible to grow nitride semiconductor layers ofgood crystal quality with a high productivity. These semiconductorlayers may be formed of semiconductor materials known in the art, forexample, nitride semiconductor materials. For example, in the case of ablue light-emitting LED, the n-type layer 121 may be formed of GaN dopedwith an n-type impurity (e.g., Si), the active layer 122 is formed ofIn_(x)Al_(y)Ga_(1-x-y)N (where 0≦x, 0≦y, x+y≦1) with or without dopant,and the p-type layer 123 may be formed of GaN doped with a p-typeimpurity (e.g., Mg). Compound semiconductors such as ZnSe may also beused. If the semiconductor material is a compound semiconductormaterial, the emission wavelengths can be adjusted by the mixed crystalratio.

The p-electrode 13 on the light-emitting device 10 is preferably formedof an electrically conductive material which can reflect the light fromthe light-emitting device toward the light-transmissive substrate 11.Such a conductive material includes, for example, a single metal such asAg, Al or Rh, an Rh—Ir alloy, or a Ti/Al/Ni/Au laminate with Auconstituting the outermost layer. The n-electrodes 14 a and 14 b mayeach be formed of a laminate such as a Ti/Al/Ni/Au laminate with Auconstituting the outermost layer, a W/Al/W/Pt/Au laminate with Auconstituting the outermost layer, or an Ni—Si—Cu alloy/W/Pt/Au/Nilaminate with Ni constituting the outermost layer.

In order to realize a white light-emitting apparatus, a bluelight-emitting device may be used as the light-emitting device 10, and aphosphor material which can be excited by the blue light from the bluelight-emitting device to emit yellow light, such as YAG phosphormaterial (rare earth aluminate phosphor activated mainly by a lanthanoidelement such as Ce) may be contained in the sealing member 40, forexample. In this case, the YAG phosphor partially absorbs the lightemitted from the blue light-emitting device to emit yellow light, whichis complementary to the blue light. The yellow light is mixed with theblue light from the blue light-emitting device, turning into whitelight, which outgoes outside from the light-emitting apparatus.Alternatively, a phosphor which can be excited by the blue light fromthe blue light-emitting device to emit red light, such as Eu and/orCr-activated nitrogen-containing CaO—Al₂O₃—SiO₂ phosphor, may be used asa phosphor to be contained in the sealing member 40. In this case, thephosphor partially absorbs the light emitted from the bluelight-emitting device to emit red light, which is complementary to theblue light. The red light is mixed with the blue light from the bluelight-emitting device, turning into white light, which outgoes outsidefrom the light-emitting apparatus.

Returning to FIG. 1, the supporting board 20 comprises an insulatingsubstrate 23, and a positive electrode 21 and two negative electrode 22a and 22 b, formed on the substrate 23. These electrodes 21, 22 a and 22b are formed, for example, as parts of a wiring pattern (notillustrated). The p-electrode 13 on the light-emitting device 10 faces,or opposes to, the positive electrode 21, while the two n-electrodes 14a and 14 b face, or oppose to, the two negative electrodes 22 a and 22b, respectively. The p-electrode 13 and the positive electrode 21,opposing to each other, are electrically connected through a bondingmember 30 a. On the other hand, the n-electrode 14 a and the negativeelectrode 22 a, opposing to each other, are electrically connectedthrough a bonding member 30 b, while the n-electrode 14 b and negativeelectrode 22 b, opposing to each other, are electrically connectedthrough a bonding member 30 c. The surface of the insulating substrate23 may be covered with an insulating material, except for the portionson which the electrodes 21, 22 a and 22 b are formed, but is usuallyexposed, except for the portions on which the electrodes 21, 22 a and 22b.

The insulating substrate 23 may be formed of a ceramic material such asalumina (Al₂O₃) or AlN. As the supporting board 20, use may be made of alead frame type one, which comprises an insulating substrate formed of athermoplastic or a thermosetting resin, on which a lead frame is formed.The surface of the lead frame, other than those surface portions whichshould be exposed so as to act as the electrodes, is covered with aresin. In this case, it is preferable to use materials small in thedifference in thermal expansion coefficient. Such materials canalleviate the thermal stress generated between the supporting board andthe light-emitting device during manufacture or use.

The material for the positive and negative electrodes 21, 22 a and 22 bis not limited, as long as it has an electrical conductivity. It ispreferable to use Au, or a silver white metal, in particular, Ag or Al,which has a high reflectivity. Such a material reflects the light fromthe light-emitting device in the direction opposite to the supportingboard, enhancing the light extraction efficiency of the light-emittingapparatus, if the positive and/or negative electrode is slightly exposedfrom the bonding members. In the case where a metal is used as anelectrically conductive material, the metal is preferably selected inview of adhesion with the bonding member or wettability with the bondingmember. One embodiment of a method for forming the positive and negativeelectrodes includes forming a photoresist pattern on those areas of theinsulating substrate of the supporting board where the electrodes arenot formed, and depositing a layer or layers of conductive material, forexample, a Ti layer in thickness of 10 nm and an Au layer in thicknessof 1 μm thereon, by a suitable method such as electron beam deposition,sputtering or plating. Thereafter, the photoresist pattern is removed,and the conductive materials formed thereon are lifted off at the sametime. As the negative electrodes, use may be also made of a laminatesuch as Ti/Au, Ni/Au, or Al/Au. Usually, the positive and negativeelectrodes are formed of the same conductive material with the samethickness at the same time.

Further, the supporting board 20 may be a co-fired board, which can beprepared by forming electrodes on a green insulating sheet (a pastecontaining particles of insulating material and a binder), for example,a green ceramic sheet, and baking the sheet, or a post-fired board,which can be prepared by baking the green insulating sheet, and thenforming electrodes on the baked insulating sheet (substrate). Theco-fired board can be mass-produced at a low cost, though it is slightlyinferior in the electrode pattern accuracy.

The bonding members 30 a-30 c may be any bonding members havingelectrical conductivity, and may be formed from a metal which can bemelted by heating, an electrically conductive paste, a solder pastematerial, sinterable Ag particles, a paste having anisotropicconductivity, or the like. Particularly, taking the wettability with,and adherence to, the electrodes on the light-emitting device and on thesupporting board into consideration, it is preferable to use an alloycontaining any of Au, Ag, Cu, Si, Sn, Pb and In, in particular, aeutectic material selected from AuSn, SnAgCu, AuSi, SnAgBi, SnAgBiCu,SnCu, SnBi and SnPbIn. Such a eutectic material can create eutecticbond.

The sealing member 40 is preferably arranged such that the distancebetween the outer edge of the light-emitting device 10 and the outerperiphery of the sealing member are substantially equal in the planeincluding the surface of the light-emitting device. This arrangementmakes it possible to make the light-emitting plane of the device small,leading to a uniform emission. The shape of the sealing member 40 may beany suitable shape, such as convex, concave, dome, or a semi-ellipse,cube or triangular prism viewed from the light emission observationplane. For example, if the sealing member 40 is shaped into a convexlens or concave lens, a lens effect can be obtained. The sealing member40 may be formed of an organic material such as an epoxy resin, anacrylic resin, an imide resin or a silicone resin, or an inorganicmaterial such as a glass, all of which is superior in light fastness andin light transmissivity. Further, the sealing member 40 may contain alight-diffusing material (particles) such as aluminum oxide, bariumoxide, barium titanate, silicon oxide or the like, in order to diffusethe light from the light-emitting device. In addition, the sealingmember 40 may be added with a coloring agent so as to have a filteringeffect to cut the outside light and to cut unnecessary wavelengths ofthe light from the light-emitting device. Furthermore, the sealingmember 40 may contain a phosphor material excited by the light emittedfrom the light-emitting device to emit fluorescence, as described above.Also, the sealing member 40 may contains fillers which can alleviateinternal stresses within the sealing resin.

Referring now to FIG. 3, the light-emitting device 10 is a quadrangle inplan in this embodiment, but may be of the other polygon, an ellipsoid,a circle in plan. The pair of n-electrodes (main n-electrodes) 14 a and14 b are disposed on the both sides of the p-electrode 13 with thep-electrode 13 centered. In other words, the two n-electrodes aredisposed with the p-electrode 13 therebetween. The p-electrode 13 issignificantly larger than the n-electrodes 14 a and 14 b, in order toincrease the light-emitting efficiency of the light-emitting device 10.The p-electrode 13 is, for example, of a quadrangular shape in whicheach of the two opposing sides of the quadrangle is curved inwardly,describing an arc. That is, the p-electrode 13 has a constrictedportion. On the other hand, each of the main n-electrodes 14 a and 14 bis of a semi-elliptic shape, and these two n-electrodes are in linesymmetry with respect to that center line of the above-noted quadranglewhich is orthogonal to the line I-I. Further, the p-electrode 13 isarranged spaced apart from each of the main n-electrodes 14 a and 14 bby a distance B (see FIG. 1). Further, in order to enhance thelight-emitting efficiency, very fine auxiliary n-electrodes 14 c and 14d in the form of an arc may be formed, extending from the mainn-electrodes 14 a and 14 b into the region of the p-electrode 13.Needless to say, there auxiliary n-electrodes are not contacted with thep-electrode 13. It should be noted that the n-electrodes are often madeas small as possible and at the same time, and the distance between thep- and n-electrodes is minimized, in order to obtain the possiblelargest light emission area of the light-emitting apparatus. However,the p and n-electrodes are required to be spaced apart by an appropriatedistance to prevent short-circuiting therebetween. Incidentally, asshown in FIG. 3, the p-electrode 13 is formed, substantially entirelycovering the electrode formation plane of the device 10, except forthose portions on which the n-electrodes are formed.

Referring to FIG. 4, the positive electrode 21 on the supporting board20 is of a quadrangular shape in which each of the central portions ofthe two opposing sides of the quadrangle is curved inwardly, describingan arc, like the p-electrode 13 on the light-emitting device 10. Thatis, the positive electrode 21 has a constricted portion. On the otherhand, each of the negative electrodes 22 a and 22 b is of asemi-elliptic shape, like the main n-electrodes of the light-emittingdevice 10. Further, the positive electrode 21 is arranged spaced apartfrom each of the negative electrodes 22 a and 22 b by a distance A (seealso FIG. 1). Incidentally, in order to illustrate the opposed state ofthe positive and negative electrodes 21, 22 a and 22 b, and theelectrode formation plane of the light-emitting device 10 in FIG. 3, theouter periphery of the electrode formation plane of the light-emittingdevice 10 is shown by the dashed line C in FIG. 4. Here, in the presentinvention, the electrode formation plane of the light-emitting devicerefers to a surface region in which the p- and n-electrodes are formed,corresponds to the surface of the substrate of the light-emittingdevice, and substantially corresponds to the surface of the n-typelayer. More specifically, the electrode formation plane of thelight-emitting device 10 is a plane observed when the p-type layer 123on which the p-electrode 13 is formed and the n-type layer 121 on whichthe n-electrodes 14 a and 14 b are formed, of the semiconductor laminatestructure 12, is viewed in plan, and is considered as a plane, thoughthe p-type layer 123 protrudes from the n-type layer 121. Further, theelectrode formation plane of the supporting board is a surface region onthe insulating substrate in which the positive and negative electrodesare formed, and which is positioned within a surface region on theinsulating substrate, opposing to the electrode formation plane of thelight-emitting device. Usually, the electrode formation planes of thelight-emitting device and the supporting board have the substantiallythe same surface area. In other word, usually, the electrode formationplane of the supporting board coincides with a plane formed byprojecting the image of the electrode formation plane of thelight-emitting device vertically onto the surface of the insulatingsubstrate with the same magnification.

More specifically, the positive electrode 21 on the supporting board 20is disposed such that it is positioned within that surface region on theinsulating substrate 23 which opposes to the p-electrode 13 of thelight-emitting device 10 (in other words, within a plane formed byprojecting the image of the p-electrode 13 vertically onto the surfaceof the insulating substrate 23 with the same magnification. In addition,the positive electrode 21 has a smaller width than that of thep-electrode 13 in the cross-section along the line I-I which extendthrough the main n-electrodes and the p-electrode within the widthregion of the p-electrode of the light-emitting device (see FIG. 1).

On the other hand, the negative electrodes 22 a and 22 b have the sameareas with the n-electrodes 14 a and 14 b, respectively, and arearranged such that they oppose to the n-electrodes 14 a and 14 b withthe same widths in the cross-section along the line I-I. In other words,the bonding area of the positive electrode 21 on the supporting boardwith the bonding member 30 a is smaller than the bonding area of thep-electrode 13 on the light-emitting device 10 with the bonding member30 a, while the bonding areas of the negative electrodes 22 a and 22 bwith the bonding members 30 b and 30 c are the same as the bonding areasof the n-electrode 14 a and 14 b with the bonding member 30 b and 30 c,respectively. Further, in the cross-section along the line I-I, thedistance A between the positive electrode and each of the negativeelectrodes is longer than the distance B between the p-electrode andeach of n-electrodes. The spaces between the positive and negativeelectrodes on the supporting board oppose to the spaces between the p-and n-electrodes on the light-emitting device, respectively.

Incidentally, it is preferable that the center of the positive electrode21 of the supporting board 20 substantially coincides with the center ofthe p-electrode 11 of the light-emitting device 10. With thisarrangement, it is possible to fix the light-emitting device 10 on thesupporting board 20 more accurately and stably. Further, in thisembodiment, it is preferable that the periphery of the electrodeformation plane of the light-emitting device 10 substantially coincideswith the periphery of the electrode formation plane of the supportingboard 20. With this arrangement, the electrodes on the light-emittingdevice can be accurately disposed with respect to the electrodes on thesupporting board. In a specific embodiment, the light-emitting device 10has an electrode formation plane of a quadrangular planar shape, and thep-electrode 11 thereon and the positive electrode 21 of the supportingboard have a deformed quadrangular planar shape as described previously.In this specific embodiment, the four corners of the electrode formationplane of the light-emitting device 10 are arranged so as tosubstantially coincide with the four corners of the positive electrode21 of the supporting board 20, respectively.

Here, one embodiment of a method of fabricating a semiconductorlight-emitting apparatus according to the present invention will bedescribed with reference to FIG. 1. The fabrication method comprisessupplying a paste comprising a bonding material (e.g., a solder pastecontaining the eutectic material described above) onto the substantiallyentire surface of the electrode formation plane of the supporting board20, including the positive electrode 21 and the negative electrodes 22 aand 22 b, by means of a dispenser or by stamping, contacting thelight-emitting device with the solder paste such that the p-electrode 13and the main n-electrodes 14 a and 14 b oppose to the positive electrode21 and negative electrodes 22 a and 22 b, respectively, and heating andmelting (reflowing) the paste and hence the bonding material. This heatmelting can be carried out in a reflow furnace. The melted bondingmaterial wets strongly with the conductive material constituting theelectrodes, but does not substantially wet the (compound) semiconductorsand the insulating materials. Thus, the melted bonding material does notextend onto the exposed surface of the insulating substrate 23 (orrepelled by the insulating material). In addition, the melted bondingmaterial wets the entire surface of the p-electrode 13 and the entiresurface of the n-electrode 14 a and 14 b (as well as the n-electrode 14c and 14 d), but does not extend onto (or repelled by) the semiconductorlayer or layers exposed from these electrodes (or the insulatingprotective film 15 if it is formed). The protective film 15 repels theconductive paste more than the compound semiconductors. In this way, thebonding members 30 a-30 c bond with the positive and negative electrodeson the supporting board 20 and with the p- and n-electrodes on thelight-emitting device 10, respectively. The melted bonding material issolidified by cooling into the bonding members 30 a to 30 c.

As described above, if the width of the constricted portion of thepositive electrode 21 on the supporting board 20 is smaller than thewidth of the constricted portion of the p-electrode 13 on thelight-emitting device 10, the bonding member 30 a bonding the positiveelectrode 21 and the p-electrode 13 has a side tapered in thecross-section along the line I-I, as illustrated in FIG. 1. As a result,those electrodes on the light-emitting device and on the supportingboard which require an electrical connection can be bonded by thebonding members, as desired, and those electrodes on the light-emittingdevice and on the supporting board which must not be electricallyconnected are prevented from short-circuiting caused by the bondingmembers. Incidentally, if the bonding members 30 a-30 c are made from,for example, an AuSn solder, the electromigration of Sn is relativelyreadily generated during lightening of the apparatus. However, when thebonding members are formed so as to have a tapered side face as in thisembodiment, those electrodes which must not be electrically connectedcan be prevented from short-circuiting if the electromigration isgenerated during the lightening of the light-emitting apparatus.

Further, since the periphery of the electrode formation plane of thelight-emitting device 10 substantially coincides with the periphery ofthe electrode formation plane of the supporting board 20, the electrodeson the light-emitting device 10 can be accurately positioned withrespect to the electrodes on the supporting board 20. Thus, thoseelectrodes on the light-emitting device and on the supporting boardwhich require an electrical connection can be bonded by the bondingmembers, as desired, and those electrodes on the light-emitting deviceand on the supporting board which must not be electrically connected areprevented from short-circuiting caused by the bonding members.

In order to more assuredly establish the self-alignment noted above, itis preferable to appropriately set the distances A between the positiveelectrode 21 and the negative electrodes 22 a and 22 b on the supportingboard 20, the distances B between the p-electrode 13 and the n-electrode14 a and 14 b of light-emitting device 10, the distance between thep-electrode 13 and the positive electrode 21 or the thickness of thebonding members, and the thickness of the electrodes, which will bedescribe below.

The distances A between the positive electrode 21 and the negativeelectrodes 22 a and 22 b on the supporting board are preferably setwithin a range of 10 μm or more, but 150 μm or less, more preferablywithin a range of 10 μm or more, but 40 μm or less. Further, thedistances B between the p-electrode 13 and the n-electrodes 14 a and 14b on the light-emitting device 10 are preferably set within a range of10 μm or more, but 40 μm or less. In a particular case where thesupporting board is a co-fired ceramic board, each of the distances Abetween the positive and negative electrodes is preferably 50 μm ormore, but 150 μm or less. In this case, the self-alignment will beestablished more assuredly, and the generation of the electromigrationwill be further suppressed.

When the bonding members are formed of a solder, the thickness of thesolder (or more precisely, the distance between the p-electrode 13 andthe positive electrode 21) is preferably more than 10 μm, particularly20 μm or more, in view of bondability with the electrodes. If thethickness of the solder is 10 μm or less, voids are generated in thesolder material which is flattened out when the light-emitting device isplaced on the supporting board, tending to result in poor bonding withthe electrodes. The thickness of the solder is preferably 40 μm or less.

Further, the thickness of the each of the electrodes 21 and 22 on thesupporting board 20 is preferably set within a range of 5 μm or more,but 50 μm or less, particularly within a range of 10 μm or more, but 30μm or less, in view of bondability with the bonding members. If thethickness of these electrodes is smaller than 5 μm, the solder material,which is flattened out when the light-emitting device is placed on thesupporting board, flows on to the supporting board, resulting indecrease in the amount of solder used for bonding, leading to reductionin thickness of the solder. Further, if the thickness of theseelectrodes is larger than 50 μm, the solder material, which is flattenedout when the light-emitting device is placed on the supporting board,flows on to the supporting board, generating short-circuiting betweenthose electrodes which must not be electrically connected.

In addition, in order to establish the above-noted self-alignment moreassuredly, it is preferable that the proportion of ratio of the bondingarea of the positive electrode 21 with the bonding member 30 a, or morebriefly, the surface area of the positive electrode 21, to the bondingarea of the p-electrode with the bonding member 30 a, or more briefly,the surface area of the p-electrode 13 is set appropriately. In thepresent invention, the bonding area proportion or ratio noted above ispreferably 50% or more, but 100% or less (the bonding area ratio of 100%means that the bonding area of the positive electrode 21 with thebonding member 30 a is equal to the bonding area of the positiveelectrode 21 with the bonding member 30 a), more preferably 85% or more,but 100% or less. If the bonding area ratio is 85% or more, anadditional advantage that the heat releasability can be enhanced as inthe case of the bonding area ratio of 100% can be obtained.

FIG. 5 is a graph illustrating a relationship between a bonding areaproportion or ratio described above and a thermal resistance ratio.Here, the bonding area ratio is a ratio of the bonding area of thepositive electrode 21 with the bonding member 30 a (or the surface areaof the positive electrode 21) to the bonding area of the p-electrode 13with the bonding member 30 a (or the surface area of the p-electrode13), in a light-emitting apparatus having the structure illustrated inFIG. 1. The thermal resistance ratio is a ratio of a thermal resistanceat each bonding area ratio to a thermal resistance at the bonding arearatio of 100%. Note that each of the p-electrode and the positiveelectrode was a laminate with the uppermost layer being formed of Au,and the bonding members were made of AuSn. As can be seen from FIG. 5,it was confirmed that when the bonding area ratio is 85% or more, theheat releasability can be enhanced as in the case of the bonding arearatio of 100%.

Variation of First Embodiment

FIG. 6 is a plan view illustrating another electrode pattern on theelectrode formation plane of the light-emitting device illustrated inFIG. 1. In this electrode pattern, the p-electrode 13, and the pair ofmain n-electrodes 14 a and 14 b are the same as those illustrated inFIG. 3. However, there are additionally formed a fine auxiliaryn-electrode 14 e extending linearly from each of the main n-electrodes14 a and 14 b toward the inside of p-electrode region, and two fineauxiliary n-electrode 14 f and 14 g which are symmetrical with respectto the auxiliary n-electrode 14 e, and extend from each of the mainn-electrodes 14 a and 14 b, each describing an arc. It is preferablethat the electrode formation plane of the light-emitting device 10 iscovered by an insulating protective film (not shown in FIG. 6) similarto the insulating protective film 15 illustrated in FIGS. 2 and 3. Withthis embodiment, the light-emitting efficiency can be further enhanced,since the number of n-electrodes is more than the first embodiment.

Second Embodiment

FIG. 7 is a cross-sectional view schematically illustrating the mainpart of a semiconductor light-emitting apparatus according to a secondembodiment of the invention. The second embodiment differs from thefirst embodiment in that the surface area of each of the negativeelectrode 22 a′ and 22 b′ of the supporting board 20 is smaller than thesurface area of each of the n-electrode 14 a and 14 b of thelight-emitting device, and that that side face of each of the negativeelectrodes 22 a′ and 22 b′ which faces the positive electrode 22 isretracted outwardly from that side face of each of the n-electrode 14 aand 14 b which faces the p-electrode 13. Thus, the bonding area of thenegative electrodes 22 of the supporting board with the bonding member30 a is smaller than the bonding area of the n-electrode 14 a, 14 b ofthe light-emitting device with the bonding members 30 b′, 30 c′. Withthis arrangement, the same advantages as described with reference to thefirst embodiment. However, the distance between the positive electrode21 and each of the negative electrodes 22 a′ and 22 b′ of the supportingboard becomes larger. In addition, in the cross-section along the centerline extending through the pair of n-electrodes and the p-electrode ofthe light-emitting device (the center line corresponding to the line I-Iof FIG. 3), the side faces of the bonding members 30 b′ and 30 c′bonding the n-electrode 14 a and 14 b of the light-emitting device withthe negative electrodes 22 a and 22 b of the supporting board are formedtapered. Thus, the short-circuiting noted above is more assuredlyprevented.

Third Embodiment

FIG. 8 is a cross-sectional view schematically illustrating asemiconductor light-emitting apparatus according to a third embodimentof the invention. FIG. 9 is a plan view illustrating an electrodepattern on the electrode formation plane of the light-emitting device10′ illustrated in FIG. 8. FIG. 10 is a plan view illustrating anelectrode pattern on the electrode formation plane of the supportingboard illustrated in FIG. 8. Here, FIG. 8 corresponds to a cross-sectionalong the line VIII-VIII extending the n-electrode and the pair ofp-electrodes and the center of the electrode formation plane.

The differs from the first embodiment in that an additional mainn-electrode 14 f is arranged at the central portion of the electrodeformation plane of the light-emitting device 10′, in addition to themain n-electrodes 14 a and 14 b (see FIG. 9), that the p-electrode isseparated into a pair of p-electrodes 13 a and 13 b with these mainn-electrodes therebetween, and that a pair of positive electrode 21 aand 21 b, and a negative electrode 22′ are formed on the insulatingsubstrate 23 of the supporting board 20, opposing to the a pair ofp-electrode 13 a and 13 b. and the n-electrodes 14 f, respectively.Here, the total area of the p-electrodes 13 a and 13 b is larger thanthe total area of the main n-electrodes, in order to enhance thelight-emitting efficiency. Each of the p-electrodes 13 a and 13 b is ofquadrangular planar shape, and extends to the four corner portions ofthe electrode formation plane of the light-emitting device. The mainn-electrode 14 f is formed in a substantially hexagonal planar shape atthe central portion of the electrode formation plane of thelight-emitting device. Further, two fine auxiliary n-electrodes 14 g areformed, extending from the central main n-electrode 14 f toward theregions of the p-electrodes 13 a and 13 b, respectively, and two fineauxiliary n-electrodes 14 h are formed, extending from the n-electrode14 f toward the main n-electrodes 14 a and 14 b. Although notillustrated in FIGS. 8 and 9, an insulating protective film similar tothe insulating protective film 15 illustrated in FIG. 2 is formed on theelectrode formation plane of the light-emitting device 10. Incidentally,as illustrated in FIG. 9, the pair of p-electrodes covers the surface ofthe electrode formation plane substantially entirely, except for thosesurface portions on which the n-electrodes are formed.

On the other hand, the positive electrodes 21 a and 21 b of thesupporting board 20″ are formed in a rectangular planar shape, andoppose to the p-electrodes 13 a and 13 b. Also, the negative electrode22′ is formed in a rectangular planar shape at the central band regionof the electrode formation plane of the supporting board. In thecross-section along the line VIII-VIII, each of the positive electrodes21 a and 21 b has a width narrower than the width of each of thep-electrode 13 a and 13 b. In addition, the side face of each of thepositive electrodes 21 a and 21 b which faces the negative electrode 14f is retracted outwardly from that side face of each of the p-electrodes13 a and 13 b which faces the n-electrode 14 f. Further, the negativeelectrode 22′ opposes to the n-electrode 14 f with the same width (orwith a width narrower than the n-electrode 14 f), in the cross-sectionalong the line VIII-VIII.

Here, the bonding area of the positive electrodes 21 a and 21 b with thebonding member 30 e and 30 f are indicated as hatched areas in FIG. 8.Further, in order to illustrate the opposed state between the electrodeformation plane of the supporting board 20″ and the electrode formationplane of the light-emitting device 10′, the periphery of the electrodeformation plane of the light-emitting device 10 is indicated by thedashed line C in FIG. 9.

Variation of Third Embodiment

In the third embodiment, three (or more) fine auxiliary n-electrodes maybe formed, extending from the central main n-electrode 14 f radiallyinto each of the regions of the p-electrodes 13 a and 13 b. With thisarrangement, the light-emitting efficiency can be further enhanced,since the number of the n-electrodes is larger than the thirdembodiment.

The present invention will be described below by way of an Example. Thepresent invention should not be limited to this Example. Needless tosay, various modifications are possible.

Example 1

In a light-emitting apparatus of the structure illustrated in FIG. 1,the n-type semiconductor layer 121 of the light-emitting device isformed of Si-doped GaN, the active layer 122 is formed of InGaN, and thep-type semiconductor layer 123 is formed of Mg-doped GaN. The supportingboard 20 is a co-fired alumina board. Each of the positive electrode 21and the negative electrodes 22 a, 22 b on the supporting board 20 isformed of gold (Au), and each distance A is 100 μm. Each of thep-electrode 13 and the n-electrodes 14 a, 14 b on the light-emittingdevice 10 is formed of a Ti/Al/Ni/Au laminate with Ti contacting thesemiconductor layer, and each distance B is 40 μm. The distance betweenlower surface of the electrodes on the supporting board 20 and the lowersurface of the p-electrode 13 was 20 μm. Each bonding member wasprepared from an AuSn solder, and each bonding member had a thickness of20 μm. The thickness of each of the electrodes 21, 22 a and 22 b was 20μm. The bonding area of the positive electrode 21 with the bondingmember 30 a is 90% of the bonding area of the p-electrode 13 with thebonding member 30 a. This light-emitting apparatus was fabricated by themethod described previously. With this arrangement, the apparatus couldbe fabricated with good self-alignment, and the electromigration couldbe suppressed assuredly.

The light-emitting apparatus of the present invention can be used invarious fields, which require a light emission with a high output powerand a high reliability, including a lighting device for vehicles.

What is claimed is:
 1. A method of fabricating a semiconductor lightemitting apparatus comprising a semiconductor light-emitting devicehaving an electrode formation plane and comprising p- and n-electrodesin the electrode formation plane; a supporting board comprising aninsulating substrate which has an electrode formation planecorresponding to the electrode of the light-emitting device and on whichpositive and negative electrodes are formed in the electrode formationplane thereof so as to oppose to the p- and n-electrodes, respectively;and bonding members bonding the p- and n-electrodes with the positiveand negative electrodes, respectively, the method comprising: supplyinga bonding material in a paste state onto the electrode formation planeof the supporting board, including the positive and negative electrodes;placing the light-emitting device on the bonding material such that thep- and n-electrodes of the light-emitting device contact the bondingmaterial; and heating and melting the bonding material, thereby bondingthe p- and n-electrodes on the light emitting device with the positiveand negative electrodes on the supporting board, respectively, whereinthe electrode formation plane is of a quadrangular shape, and thep-electrode of the light-emitting device extends to the four corners ofthe electrode formation plane.
 2. The method according to claim 1,wherein the electrode formation plane of the light-emitting devicesubstantially coincides with the electrode formation plane of thesupporting board.
 3. The method according to claim 1, wherein thepositive electrode of the supporting board has a width smaller than thatof the p-electrode of the light-emitting device, in a cross sectionextending through the p- and n-electrodes of the light-emitting device.4. The method according to claim 1, wherein the bonding material isformed of a eutectic material including an AuSn.
 5. The method accordingto claim 4, wherein the supporting board comprises an insulatingsubstrate formed of a ceramic material, and a positive electrode and twonegative electrodes, formed on the substrate.
 6. The method according toclaim 1, wherein the heating and melting is carried out by reflowing. 7.The method according to claim 1, wherein a pair of n-electrodes aredisposed on both sides of the p-electrode with the p-electrode centered.8. The method according to claim 7, wherein the n-electrodes on thelight-emitting device are disposed at a central portion of the electrodeformation plane of the light-emitting device.
 9. The method according toclaim 1, wherein the positive electrode on the supporting board isspaced apart from the negative electrode on the supporting board by adistance within a range of 10 μm or more, but 40 μm or less.
 10. Themethod according to claim 1, wherein the p-electrode on thelight-emitting device is spaced apart from the n-electrode on thelight-emitting device by a distance within a range of 10 μm or more, but40 μm or less.
 11. The method according to claim 1, wherein each of thepositive and negative electrodes on the supporting board has a thicknesswithin a range of 5 μm or more, but 50 μm or less.
 12. The methodaccording to claim 1, wherein each of the positive and negativeelectrodes on the supporting board has a thickness within a range of 10μm or more, but 30 μm or less.
 13. A method of fabricating asemiconductor light emitting apparatus comprising a semiconductorlight-emitting device having an electrode formation plane and comprisingp- and n-electrodes in the electrode formation plane; a supporting boardcomprising an insulating substrate which has an electrode formationplane corresponding to the electrode of the light-emitting device and onwhich positive and negative electrodes are formed in the electrodeformation plane thereof so as to oppose to the p- and n-electrodes,respectively; and bonding members bonding the p- and n-electrodes withthe positive and negative electrodes, respectively, wherein the positiveelectrode of the supporting board has a width smaller than that of thep-electrode of the light-emitting device, in a cross section extendingthrough the p- and n-electrodes of the light-emitting device, the methodcomprising: supplying a bonding material in a paste state onto theelectrode formation plane of the supporting board, including thepositive and negative electrodes; placing the light-emitting device onthe bonding material such that the p- and n-electrodes of thelight-emitting device contact the bonding material; and heating andmelting the bonding material, thereby bonding the p- and n-electrodes onthe light emitting device with the positive and negative electrodes onthe supporting board, respectively.
 14. The method according to claim13, wherein the positive electrode on the supporting board is spacedapart from the negative electrode on the supporting board by a distancewithin a range of 10 μm or more, but 40 μm or less.
 15. The methodaccording to claim 14, wherein the p-electrode on the light-emittingdevice is spaced apart from the n-electrode on the light-emitting deviceby a distance within a range of 10 μm or more, but 40 μm or less. 16.The method according to claim 15, wherein each of the positive andnegative electrodes on the supporting board has a thickness within arange of 5 μm or more, but 50 μm or less.
 17. The method according toclaim 15, wherein each of the positive and negative electrodes on thesupporting board has a thickness within a range of 10 μm or more, but 30μm or less.
 18. The method according to claim 13, wherein thep-electrode on the light-emitting device is spaced apart from then-electrode on the light-emitting device by a distance within a range of10 μm or more, but 40 μm or less.
 19. The method according to claim 13,wherein each of the positive and negative electrodes on the supportingboard has a thickness within a range of 5 μm or more, but 50 μm or less.20. The method according to claim 13, wherein each of the positive andnegative electrodes on the supporting board has a thickness within arange of 10 μm or more, but 30 μm or less.
 21. A method of fabricating asemiconductor light emitting apparatus comprising a semiconductorlight-emitting device having an electrode formation plane and comprisingp- and n-electrodes in the electrode formation plane; a supporting boardcomprising an insulating substrate which has an electrode formationplane corresponding to the electrode of the light-emitting device and onwhich positive and negative electrodes are formed in the electrodeformation plane thereof so as to oppose to the p- and n-electrodes,respectively; and bonding members bonding the p- and n-electrodes withthe positive and negative electrodes, respectively, wherein a pair ofn-electrodes are disposed on both sides of the p-electrode with thep-electrode centered, the method comprising: supplying a bondingmaterial in a paste state onto the electrode formation plane of thesupporting board, including the positive and negative electrodes;placing the light-emitting device on the bonding material such that thep- and n-electrodes of the light-emitting device contact the bondingmaterial; and heating and melting the bonding material, thereby bondingthe p- and n-electrodes on the light emitting device with the positiveand negative electrodes on the supporting board, respectively.
 22. Themethod according to claim 21, wherein the n-electrodes on thelight-emitting device are disposed at a central portion of the electrodeformation plane of the light-emitting device.
 23. A method offabricating a semiconductor light emitting apparatus comprising asemiconductor light-emitting device having an electrode formation planeand comprising p- and n-electrodes in the electrode formation plane; asupporting board comprising an insulating substrate which has anelectrode formation plane corresponding to the electrode of thelight-emitting device and on which positive and negative electrodes areformed in the electrode formation plane thereof so as to oppose to thep- and n-electrodes, respectively; and bonding members bonding the p-and n-electrodes with the positive and negative electrodes,respectively, wherein the bonding material is formed of a eutecticmaterial including an AuSn, and wherein the supporting board comprisesan insulating substrate formed of a ceramic material, a positiveelectrode, and two negative electrodes, formed on the substrate, themethod comprising: supplying a bonding material in a paste state ontothe electrode formation plane of the supporting board, including thepositive and negative electrodes; placing the light-emitting device onthe bonding material such that the p- and n-electrodes of thelight-emitting device contact the bonding material; and heating andmelting the bonding material, thereby bonding the p- and n-electrodes onthe light emitting device with the positive and negative electrodes onthe supporting board, respectively.
 24. The method according to claim23, wherein the heating and melting is carried out by reflowing.